An energy irradiation apparatus is used to eliminate or to cure a lesion in a living body by inserting an elongated insertion portion into the living body through a lumen or a small incision made in the living body, selectively irradiating the lesion with energy, and causing heating, denaturation, necrosis, coagulation, cauterization, or vaporization of the tissue of the lesion. Such an energy irradiation apparatus is generally designed to directly irradiate a lesion located on or near the surface layer of living tissue with energy.
In addition, a technique of irradiating a deep region in living tissue with energy is also known, which is used to cure a lesion located deep in living tissue, that is, a deep lesion, as in thermal treatment for benign prostatic hyperplasia, by directly inserting an energy irradiation portion into a deep lesion inside the prostate by puncture.
The prostate is located in the basal region of the bladder of a male, surrounding the posterior portion of the urethra. When energy irradiation treatment is to be performed for benign prostatic hyperplasia, a transurethal technique is often used. However, irradiation of energy through the urethra for a long period of time or inserting a needle-like energy irradiation portion through the urethra damages the surface of the urethra. This may cause an infectious disease through the wound.
In consideration of such a problem, an apparatus which concentrates energy having deep transmission capability against living tissue onto a deep portion while continuously moving the energy exit end portion has been proposed as an apparatus which cures only the affected part of the prostate without damaging the surface of the urethra. Such energy concentrating apparatuses are disclosed in Japanese Patent Laid-Open Nos. 11-333005, 2000-319, and 2001-46396.
According to an apparatus designed to concentrate energy having deep transmission capability against living tissue as described in each of the patent references described above, the energy irradiation end portion is periodically reciprocated to disperse energy on the surface layer of the urethra so as to preserve the tissue. On the other hand, energy is concentrated onto a deep portion as a lesion of living tissue to provide effective heating treatment.
Such an apparatus uses a reciprocating mechanism having a link. One end of the link is supported on a disk which is rotated/driven to produce periodic reciprocating motion, while the other end of the link is supported on a moving member which is reciprocated. With this structure, reciprocating motion becomes angular velocity motion. As a consequence, unbalanced velocities occur near the middle and two ends of reciprocation.
If energy irradiation is performed by using the reciprocating mechanism which produces low velocities near the two ends of reciprocation and the highest velocity near the middle, energy is radiated for a long period of time near the two ends of reciprocation. This may locally heat the surface layer of the urethra and then results in failure to preserve the surface layer tissue or results in failure to obtain a sufficient treatment effect.